Using ugen0.04 was my first thought, but that didn't help. I tried all
of the ugen0.xx ports, just to see what would happen.

FWIW the below code will tell you what all the endpoints on a ugen
device are. Unfortunately this will only work if the device is grabbed
by ugen, if another driver gets the device you cannot query it. Though,
IMHO, we should be able to, it can be useful sometimes and would allow
us to implement something like the linux lsusb command. Apologies for
the lack of error checking and so forth, this was a quick hack I threw
together when poking at a USB device...

I compiled and ran it - the only ugen device I could query was
ugen0.00. Still, lots of interesting information.